Annual report pursuant to Section 13 and 15(d)

Retirement Savings Plans (Narrative) (Details)

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Retirement Savings Plans (Narrative) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Liability to participants under deferred compensation plan $ 14,000,000.0 $ 9,500,000  
Current liability to participants under deferred compensation plan 1,700,000 1,200,000  
401(k) Profit-Sharing Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Company contributions to the plan 9,400,000 8,900,000 $ 7,700,000
Deferred Compensation Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Company contributions to the plan 500,000 400,000 $ 200,000
Other Noncurrent Assets [Member] | Deferred Compensation Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Fair value of mutual fund investments 14,000,000.0 9,500,000  
Short-term Investments [Member] | Deferred Compensation Plan [Member]      
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]      
Fair value of mutual fund investments $ 1,700,000 $ 1,200,000